High-throughput and single nucleotide resolution techniques for the determination of rna post-transcriptional modifications

ABSTRACT

Disclosed herein are methods and associated compositions and kits for identifying nucleoside modifications. Particularly exemplified herein are methods that involve inducing base misincorporation at locations in an RNA that harbor a nucleoside modification. The resulting cDNA can then be subjected to next generation sequencing to identify mutations with respect to a reference sequence. Moreover, the type of nucleoside modification can be determined based on the substitution pattern of a given nucleoside modification.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with Government Support under Grant No. R21CA175625 awarded by the National Institutes of Health and Grant No. 1649522 awarded by the National Science Foundation. The Government has certain rights to the invention.

BACKGROUND

At the moment methods for the detection of the RNA postranscriptional modifications at the single nucleotide level and high throughput are largely missing^(1, 3). RNA post-transcriptional modifications have been implicated in various cancer cell propagation such as leukemia, colorectal, endometrial, stomach, prostate and breast cancers, and they have shown to play a role in Parkinson's diseases, attention deficit disorder, addiction, epilepsy, bacterial and viral infections, including Zika^(1, 3, 4). The lack of effective techniques for the determination of the RNA post-transcriptional modification makes it challenging: (i) to investigate the function of these modifications on human disease¹, (ii) to develop novel methods for numerous diseases detection, (iii) to design and develop drugs that target the RNA post-transcriptional modifications. Presently, most techniques used for the determination of the RNA post-transcriptional modifications: (i) require the RNA molecule purification before determining its post-transcriptional modifications⁵⁻⁷, (ii) are intricate and time consuming^(5, 7, 8), (iii) have difficulty identifying the exact modified base in an RNA sequence^(6, 8). Thus, novel techniques for the determination of RNA post-transcriptional modification are of great public health, biotech and pharmaceutical industry interests.

DETAILED DESCRIPTION

Disclosed herein are methods and associated compositions and kits for identifying nucleoside modifications. Methods have been developed that involve inducing base misincorporation at locations in an RNA that harbor a nucleoside modification. This misincorporation is dictated by certain constituents provided in the reverse transcription reaction mix, namely including an amount of Mn²⁺. The resulting cDNA can then be subjected to next generation sequencing to identify mutations with respect to a reference sequence. Moreover, the type of nucleoside modification can be determined based on the substitution pattern of a given nucleoside modification. For example, if interrogation of an RNA molecule reveals a nucleoside modification at a given locus, the type of nucleoside modification can be elucidated by comparing to previously determined substitution patterns for a given modification (see e.g. Table 1 infra). Embodiments described herein are able to identify at single nucleotide resolution 10 out of 100 known post-transcriptional RNA modifications^(1, 2).

Definitions

Unless otherwise defined, all technical and scientific terms used herein are intended to have the same meaning as commonly understood in the art to which this invention pertains and at the time of its filing. Although various methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. However, the skilled should understand that the methods and materials used and described are examples and may not be the only ones suitable for use in the invention. Moreover, it should also be understood that as measurements are subject to inherent variability, any temperature, weight, volume, time interval, pH, salinity, molarity or molality, range, concentration and any other measurements, quantities or numerical expressions given herein are intended to be approximate and not exact or critical figures unless expressly stated to the contrary. Hence, where appropriate to the invention and as understood by those of skill in the art, it is proper to describe the various aspects of the invention using approximate or relative terms and terms of degree commonly employed in patent applications, such as: so dimensioned, about, approximately, substantially, essentially, consisting essentially of, comprising, and effective amount.

Generally, nomenclature used in connection with, and techniques of, cell and tissue culture, molecular biology, immunology, microbiology, genetics, protein, and nucleic acid chemistry and hybridization described herein are those well-known and commonly used in the art. The methods and techniques of the present invention generally are performed according to conventional methods well known in the art and as described in various general and more specific references, unless otherwise indicated. See, e.g., Sambrook et al. Molecular Cloning: A Laboratory Manual, 2d ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1989); Ausubel et ah, Current Protocols in Molecular Biology, Greene Publishing Associates (1992, and Supplements to 2002); Harlow and Lan, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1990); Principles of Neural Science, 4th ed., Eric R. Kandel, James H. Schwartz, Thomas M. Jessell editors. McGraw-Hill/Appleton & Lange: New York, N.Y. (2000). Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

The term “next generation sequencing” or “NGS” as used herein refers to sequencing techniques that elucidate a nucleic acid sequence by analyzing numerous fragments of that nucleic acid sequence in parallel. Examples of next generation sequencing include (i) sequencing by synthesis of single-molecule arrays with reversible terminators (e.g. Illumina/Solex approach, see S. Bennett, Solexa Ltd, Pharmacogenomics 5 (2004) 433-438; S. T. Bennett, C. Barnes, A. Cox, L. Davies, C. Brown, Toward the 1,000 dollars human genome, Pharmacogenomics 6 (2005) 373-382; and The term “RNA containing sample” as used herein refers to a sample that contains RNA to be analyzed. D. R. Bentley, Whole-genome re-sequencing, Curr. Opin. Genet. Dev. 16 (2006) 545-552)); (ii) pyrosequencing in high-sensity picoliter reactors (e.g. 454/Roche FLX system technology, M. Margulies, et al., Genome sequencing in microfabricated high-density picolitre reactors, Nature 437 (2005) 376-380); and (iii) massively parallel sequencing by ligation (e.g. ABI/SOLiD approach; J. Shendure, et al., Accurate multiplex polony sequencing of an evolved bacterial genome, Science 309 (2005) 1728-1732).

The term “modified nucleoside” as used herein refers to the nucleosides adenosine, inosine, cytidine, uridine, guanosine, or 7-deazaguanosine that have been modified from their canonical form. Examples of modifications to nucleosides include Pseudouridylation, 2′-O-methylation, and base methylation. Provided below are specific nucleoside modifications that can be identified by the method embodiments disclosed herein.

The term “presence of Mn²⁺” as used herein refers to an amount of Mn²⁺ used in a reverse transcription reaction sufficient to generate misincorporation of a nucleoside at a locus in an RNA having a nucleoside modification. In specific embodiments, the amount of Mn²⁺ comprises 0.01 mM to 40 mM in the reverse transcription reaction mixture. In a more specific embodiment, the amount of Mn²⁺ comprises 1-10 mM.

Methods

According to one embodiment, disclosed is a method for detecting an RNA post-transcriptional modification in a sample. The method involves performing a reverse transcription reaction of an RNA in the presence of Mn²⁺ to generate cDNA, wherein the Mn2+ is at a concentration sufficient to induce a base misincorporation at a location of the RNA comprising a nucleoside modification; and performing next generation sequencing on the cDNA under conditions to detect the base misincorporation.

In a specific method embodiment, the nucleoside modification detected includes of m2G (N2-methylguanosine), m3Ψ (3-methylpseudouridine), 5-hydroxylC (5-hydroxyl cytosine), m7G (7-methylguanosine), m4Cm (N4,2′-O-dimethylcytosine), m3U (3-methyluridine), m6,6 A (N6, N6-dimethyladenosine), m1G (1-methylguanosine), m6 A (N6-methyladenosine), m5U (5-methyluridine), Cm (2′-O-methylcytidine), Um (2′-O-methyluridine), Am (2′O-methyladenosine), Gm (2′-O-methylguanosine), Ψ (pseudouridine), m1A (1-methyladenosine), or a combination thereof.

In an even more specific embodiment, the nucleoside detected includes m2G (N2-methylguanosine), m3Ψ (3-methylpseudouridine), 5-hydroxylC (5-hydroxyl cytosine), m7G (7-methylguanosine), m4Cm (N4,2′-O-dimethylcytosine), m3U (3-methyluridine), m6,6 A (N6, N6-dimethyladenosine), m1G (1-methylguanosine), or a combination thereof. Further still, the nucleoside modification includes m6 A (N6-methyladenosine), m5U (5-methyluridine), Cm (2′-O-methylcytidine), Um (2′-O-methyluridine), Am (2′O-methyladenosine), Gm (2′-O-methylguanosine), Ψ (pseudouridine), m1A (1-methyladenosine), or a combination thereof.

In a specific embodiment, performing the next generation sequencing involves converting the cDNA fragments into dsDNA; fragmenting the dsDNA; and performing sequencing on the dsDNA fragments that employs pyrosequencing, sequencing by ligation or sequencing by synthesis methodologies.

In alternative embodiments, a method for detecting an RNA post-transcriptional modification in a sample involves obtaining a sample that has been prepared by already performing one or more steps in the broader method. For example, the method may involve identifying one or more mutations in a DNA nucleic acid sequence in obtained sample made as a result of subjecting a RNA to reverse transcriptase in the presence of Mn2+; wherein a locus of a mutation of the one or more mutations represents a nucleoside modification. The sample may pertain to a dsDNA library of fragments to which next generation sequencing is performed. Performing next generation sequencing on the dsDNA library of fragments may involve obtaining sequence data via pyrosequencing, sequencing by ligation or sequencing by synthesis methodologies; and aligning the sequence data to generate aligned sequence data. The aligned sequence data is then compared to a reference sequence and mutation frequencies are calculated in the aligned sequence data. In a specific embodiment, the nucleoside modification type of the nucleoside modification is determined based on a substitution pattern of the corresponding mutation.

In an alternative embodiment, a method is disclosed that involves obtaining aligned sequence data of a RNA that has been subjected to reverse transcription in the presence of Mn2+ and next generation sequencing; identifying one or more mutations in the aligned sequence data relative to a reference sequence; and determining one of the following based on the identifying step:

-   -   (i) a cell type in which the RNA was produced;

(ii) whether a cell type in which the RNA was produced is cancerous; and (iii) whether the biological source of the sample is a twin of another sample.

Compositions

Based on the discoveries provided herein, new compositions have been developed that are particularly tailored for implementation with method embodiments disclosed herein. In one example, a reverse transcriptase buffer composition is provided that includes a Tris compound; a potassium salt; a reducing agent; and a manganese salt. Examples of a Tris compound include Tris acetate or Tris hydrochloride. Examples of the manganese salt include manganese chloride or manganese acetate. An example of a reducing agent is dithiothreitol. Examples of the potassium salt include potassium chloride or potassium acetate. The reverse transcription buffer composition may alternatively include deoxynucleotide triphosphates (dNTPs). The level of individual dNTPs (e.g. A, G, C and U) may be altered to optimize the reverse transcription reaction depending on the type or brand of reverse transcriptase used.

Kits

Further, based on the discoveries disclosed herein, kits are provided which contain components specifically tailored to assist in induction of nucleoside misincorporation. In one embodiment, a reverse transcription kit is provided that includes an amount of an reverse transcription buffer composition that includes a manganese salt; and one or more of the following:

(i) an amount of an RT primer containing composition;

(ii) an amount of a dNTP containing composition; and (ii an amount of a reverse transcriptase containing composition.

Screening

The methods and discoveries disclosed herein also enable screening for agents that induce or inhibit nucleoside modifications (nucleoside modification modulator or NMM agent). For example, a screening method may involve subjecting a cell to a test agent; obtaining an RNA sample from the test agent; and determining whether the RNA sample comprises one or more nucleoside modifications by performing reverse transcription on the RNA sample in the presence of Mn²⁺ to produce a cDNA, performing next generation sequencing of the cDNA to produced aligned sequence data and identifying one or more mutations in the aligned sequence data relative to a reference sequence. The presence or absence of nucleoside modifications identified in the RNA sample can be compared to a control RNA sample, A control RNA sample is typically a corresponding RNA from same cell type but where the cell has not been subjected to the test agent. The test agent may be identified as an NMM if a number or type of nucleoside modifications in the RNA sample differs from the control RNA sample.

EXAMPLES Example 1: Identification of Post-Transcriptional Modifications in 5S, 16S and 23S Ribosomal RNA Subunits from Escherichia Coli

Results

The 30S and 50S subunit from Escherichia Coli (E. coli) were isolated using the sucrose gradient technique and purified the 5S, 16S and 23S ribosomal RNA via phenol extraction and ethanol precipiation⁹. Next, reverse transcriptase reaction was performed on the 5S, 16S and 23S ribosomal RNA in the presence of Mn²⁺ and SuperScript II enzyme. The reverse transciptase reaction was performed with six nucleotide long random primers; however, the reverse transcriptase reaction could also be performed with primer specific for an RNA molecule. In that case, the RNA molecule does not need to be separated from other RNA molecules. Subsequently, next generation sequencing (NGS) was performed to determine the sequence of cDNA product.

The analysis of the next generation sequencing data of the reverse transcriptase product shows base misincorporation at a number of previously known ribosomal RNA base modifications (Table 1). These modifications are: m2G (N2-methylguanosine), m3Ψ (3-methylpseudouridine), m4Cm (N4,2′-O-dimethylcytosine), m3U (3-methyluridine), m6,6 A (N6, N6-dimethyladenosine), m1G (1-methylguanosine).

Treatment of RNA samples with N-cyclohexyl-N-β(4-methylmorpholinium) ethylcarbodiimide p-tosylate (CMCT)¹⁰ produces adduct with G bases at position N1, U bases at position N3, and bases at positions N3 and N1^(10, 11). Treatment of the reaction mixture with NaHCO₃ (final pH 10.4) hydrolyzes all adducts formed between CMCT and the RNA bases with the exception of adducts formed between CMCT and N3 of Ψ^(10, 11). This adduct produces the termination of the reverse transcriptase reaction preformed in presence of Mg²⁺ at precisely one base before Ψ^(11, 12). The experimental data provided herein shows that in presence of Mn²⁺, the reverse transcriptase misincorporates a residue at the CMCT modified instead of stopping its polymerase reaction (Table 2, FIG. 1).

Dihydrouridine (D) treatment with CMCT followed by alkaline treatment of reaction at pH 10.4, and reverse transcriptase reaction in presence of Mn²⁺ produces a base misincorporation at the D position (Table 2, FIG. 1). CMCT is not expected to form a stable adduct with D after alkaline treatment¹¹. However, previous experiments have shown that treatment of D with alkaline solution produces base opening¹³. Hence, it is very likely the open D ring produces the base misincorporation by reverse transcriptase in presence of Mn²⁺.

Incubation of RNA with CMCT followed by alkaline treatment of the mixture at pH 10.4 also produces misincorporation by reverse transcriptase in present of Mn²⁺ at 7-methylguanosine (m7G) and 5-hydroxycytosine (5-OH C) (Table 3 and 4). CMCT does not stay bound to G or C bases after alkaline treatment¹¹, hence the misincorporation must be a consequence of alkaline treatment¹¹. In fact, alkaline treatment has shown to from an abasic site at m7G position¹⁴. Moreover, it is very likely that similar to D, alkaline treatment opens the 5-OH C ring.

Cm, Um, Am, Gm have been detected previously by performing the reverse transcriptase in presence of low amount of dNTPs¹⁴⁻¹⁶. Under this regime and in the presence of Mg²⁺, the reverse transcriptase stops one residue before the modification^(15, 16). It is expected that performing the reaction with 1-100 uM of one dNTP, 1 mM of the other three dNTPs and in presence of SuperScript II plus Mn²⁺ would produce a base misincorporation instead of a stop in the reverse transcriptase reaction at the position of the methylated nucleotide that currently do not produce a base mismatch. The misincorporation will be observed for the base that is at low concentration in the reaction mixture. Examples of modifications that we expect of observe are Cm, Um, Am, Gm and 6 methyl adenosine (m6A).

Dimethyl sulfate treatment of A and C bases produce m1A and m3C. The reverse transcriptase reaction of m1A, m3C bases in presence of Mn²⁺ have shown to produce a mismatch^(17, 18). Hence, our reverse transcriptase reactions in presence of Mn²⁺ are expected to detect the m1A, m3C modifications on RNA. There are no m1A and m3C in E. coli ribosome¹⁹, so they were not observed. There are previous studies that involved determination of m1A and m3C as mismatches from the reverse transcriptase reaction performed in presence of Mn^(2+/17, 18), however, that group was looking for artificially induced adducts compared to a control RNA, whereas embodiments herein detect naturally occurring RNA modifications. Both the detection of m2G, m3Ψ, m4Cm, m3U, m6,6 A and m1G and the simultaneous detection of m1A and m3C with those modifications is believed to be reported herein for the first time.

Materials and Methods.

Detection of m1G, m2G, m3Ψ, m4Cm, m3U, and m6,6 A.

First, the 30S and 50S ribosomal particles were isolated using sucrose gradients⁹. Subsequently, the 5S, 16S, 23S was purified from these particles using phenol extraction and ethonol precipitated. RNA form each particles were resuspended in water. Next, 100 ng of RNA was mixed with 200 ng of random six nucleotide long primers, heat at 95° C. for 1 minute, 65° C. for 5 minutes, incubate at 22° C. for 15 minutes and then place on ice. This allows the primers to anneal to RNA. The reaction buffer and 200 unit of SuperScript II enzyme (Thermo Fisher Scientific) were added to the mixture. The reaction buffer consisted of 50 mM Tris pH 8.3, 75 mM KCl, 1 mM each dNTP, 10 mM DTT, 6 mM MnCl₂. The reaction mixture was incubated at 22° C. for 10 minutes, at 42° C. for 3 hours and then the SuperScript II enzyme was killed by placing the reaction at 65° C. for 20 minutes. We use the NEB Second strand synthesis kit to convert the cDNA to dsDNA, and then the Illumina Nextera XT kit to add adapters for sequencing. However, the library preparation can be accomplished by a number of methods since the modification sites are encoded into the cDNA as mistakes

Following the sequencing reaction (MiSeQ 2×150), the adapter-trimmed reads are aligned using Bowtie 2—although any alignment program which allows for mistakes can be used. The specific alignment parameters used are [This is the ShapeMapper default for bowtie2]^(20, 21).

-   -   ‘--local’, ‘-D’, ‘20’, ‘-R’, ‘3’, ‘-N’, ‘1’, ‘-L’, ‘15’, ‘-i’,         ‘S,1,0.50’, ‘--score-min’, ‘G,20,8’, ‘--ma’, ‘2’, ‘--mp’, ‘6,2’,         ‘--rdg’, ‘5,1’, ‘--rfg’, ‘5,1’, ‘--dpad’, ‘100’, ‘--maxins’,         ‘800’, ‘-p’, ‘4’, ‘-x’,

Alignment parameters must be adjusted according to the experiment being undertaken. One essential parameter for our adjusted technique is -N 1, which allows for collecting mutations. The alignment is then written into a SAM file and parsed for mutations using the freely available ShapeMapper program²¹, which counts deletions and substitutions at each base position relative to the reference sequence, and then computes the mutation frequency [(# Deletions+Substitutions)/number of reads] at each position. Insertions are ignored by the program²¹.

The background mutation frequency was calculated by using the mean mutation frequency of the dataset after removing data points corresponding to DNA sequence variations. The DNA sequence variations are a consequence of the fact that E. coli contains 7 copies of ribosomal RNA gene and there are differences on of these genes' sequences.

It was determined that positions with a high frequency of mutations corresponded to RNA bases known from previous experiments to be post-transcriptionally modified²². Using the mutation frequencies, all the m2G, m3Ψ, m4Cm, m3U, m6,6 A, m1G modifications in the 16S and 23S ribosomal RNA were determined.

Detection of Ψ, 5-OH C, and D

The RNA was purified as described for the other modifications above. Prior to reverse transcription, 7.5 ug of RNA was incubated with ˜250 mM CMCT in a pH 8.4 buffer containing 7M urea and allowed to react at 37 C for 20 minutes. The reaction was stopped by adding an equal volume of 0.5M Acetate pH 5.5, and ethanol precipitated. The precipitate was resuspended in pH 10.4 buffer, and placed at 37 C for 3.5 hours. The reaction was again stopped with 0.5M acetate and precipitated. The precipitate was then resuspended in water and reverse transcribed, prepared into a next generation sequencing library, and sequenced. These reactions were sequenced in parallel with samples which never saw CMCT treatment. The mutations were counted as described for the other modifications in both samples as described above. However, the difference between the mutation rates in the +CMCT and untreated samples were calculated, as well as the fold change (Difference in Mutation Rate at a position divided by the mutation rate of the untreated sample at that position) for every position. Modifications were present at positions where a difference in mutation rate above 2% and a fold change at or above 10-fold were calculated (Tables 2-4).

The chemical treatment of the RNA with CMCT has been previously well characterized, however¹¹, the use of Mn²⁺ in reverse transcription and counting mutations has not been previously conducted for these modifications: Ψ, 5-OH C, and D.

Discussion

Benefits of the methods provided herein include the following: (i) the RNA molecule does not need to be purified, as the next generation sequencing can be performed and the precise RNA modifications in a mixture of RNA molecules can be achieved by using primers specific to the desired RNA, (ii) identification of a number of post-transcriptional modifications can be carried out simultaneously, (iii) the exact base in the sequence that is modified can be determined; hence, the technique allows single nucleotide resolution detection, (iv) detection of mistakes is advantageous to stops because modified nucleotides near in sequence can be identified by counting mistakes.

The experiments and data herein are the first demonstration of using reverse transcriptase reaction in the presence of Mn²⁺ for the determination of RNA post-transcriptional modifications. Kevin Weeks group aiming to determine RNA secondary and tertiary structure, chemically modified RNA, performed the reverse transcriptase reaction in presence of Mn²⁺ and identified the location of chemically modified bases by comparing via next generation sequencing the misincorporation of bases in chemically modified and unmodified RNA, the control sample²⁰. However, the Weeks group disregarded the misincorporations observed in the control chemically untreated RNA sample. They considered these misincorporations experimental noise. The present disclosure represents the first realization that the misincorporations observed in the chemically untreated RNA control sample are a consequence of the post-transcriptional modification process. Hence, present discovery involved detecting the post-transcriptional modifications in what previously was considered noise.

A new computer program was designed which was suggested to work for RNA endogenous post-transcriptional modifications. The specific modifications that the program can detect was not mentioned. The authors of that paper claimed that high background rate of mutations could be a consequence of RNA post-transcriptional modifications²³.

CONCLUSION

High-throughput techniques for the identification of RNA post-transcriptional modifications at single nucleotide resolution while determining the modifications position in the RNA sequence do not exist. Provided herein are methods to identify simultaneously at least nine classes (or at least eighteen classes) of RNA modifications via NGS. More importantly, since the present techniques can detect a methyl group, which is a relatively small group, they can also detect other more bulky RNA modifications. In other words, method embodiments can serve as a platform for the identifications of much larger classes of RNA post-transcriptional modifications.

Our method can detect ring opening in a base, and an abasic site. Future chemical methods that open a specific modified base, or form an abasic site can be used combined with our technique to determine the precisely position and relative extent of modification of a base.

TABLE 1 Modification observed in untreated ribosome sample Fold over Modifi- Mutation Substitution back- Base^(a) RNA^(b) cation^(c) Rate^(d) Pattern^(e) ground G 745 23S m1G 0.7446 Del >> T >> A~C 471 G 1835 23S m2G 0.6336 C >> Del > A~T 401 U 1915 23S m3 Ψ 0.812 A >> G >> C~Del 514 G 2445 23S m2G 0.048 C >> T~A~Del 30 Back- 23S 0.00158 ground G 966 16S m2G 0.02105 A > T > C~Del 8 G 1515 16S m2G 0.04039 A > T > C~Del 16 G 1207 16S m2G 0.06695 C >> A >> T~Del 27 U 1498 16S m3U 0.417 G > A >> C~Del 167 C 1402 16S m4Cm 0.0118 T > A~G No Del 5 A 1519 16S m6,6 A 0.168 T > Del~G > C 67 A 1518 16S m6,6 A 0.0147 T > G~Del > C 6 Back- 16S 0.0025 ground ^(a)RNA bases position on the ribosomal RNA. ^(b)RNA molecule where the modification was observed. ^(c)The type of modification as previously determined. ^(d)Rate of mutation determined as explained in the materials and method part of this document. ^(e)Substitution patterns determined from the alignments. ^(f)The ratio of the frequency of mutation at a specific ribosomal RNA position over the average frequency of mutation on the whole RNA molecule

TABLE 2 All U positions containing a difference in mutation rate > 2%. CMC Background Differences in Fold Base ^(a) RNA^(b) Modification ^(c) Mutation Rate ^(d) Mutation Rate ^(e) Mutation Rate^(f) Change^(g) U 1921 23S Ψ 0.1274 0.0004 0.1270 319 U 957 23S Ψ 0.1609 0.0011 0.1598 145 U 2584 23S Ψ 0.2706 0.0027 0.2678 98 U 2453 23S D 0.0590 0.0006 0.0584 98 U 2609 23S Ψ 0.0595 0.0008 0.0588 77 U 748 23S Ψ 0.0269 0.0004 0.0266 73 U 2461 23S Ψ 0.0724 0.0011 0.0713 65 U 2508 23S Ψ 0.0597 0.0010 0.0587 59 U 1915 23S Ψ 0.0256 0.0008 0.0247 29 U 2608 23S Ψ 0.0242 0.0011 0.0231 20 U 1508 23S None 0.0528 0.0205 0.0323 2 U 829 23S None 0.0464 0.0212 0.0252 1 ^(a) RNA bases position on the ribosomal RNA. ^(b)RNA molecule where the modification was observed. ^(c) The type of modification as previously determined. ^(d) Rate of mutation determined as explained in the materials and method part of this document. ^(e) Rate of mutation for the background sample as explained in the materials and method part of this document ^(f)Differences in the rate of mutation of the CMCT treated sample and untreated background sample. ^(g)The fold change in mutation rate caused by CMCT treatment, calculated as the ratio of the difference in mutation rates of the CMCT treated and untreated sample divided by the mutation frequency of the untreated sample.

TABLE 3 All G positions positions containing a difference in mutation rate > 2%. CMC Background Differences in Fold Base^(a) RNA^(b) Modification^(c) Mutation Rate^(d) Mutation Rate^(e) Mutation Rates^(f) Change^(g) G 2073 23S m7G 0.0795 0.0028 0.0767 27 G 2894 23S None 0.0302 0.0076 0.0226 3 ^(a)RNA bases position on the ribosomal RNA. ^(b)RNA molecule where the modification was observed. ^(c)The type of modification as previously determined. ^(d)Rate of mutation determined as explained in the materials and method part of this document. ^(e)Rate of mutation for the background sample as explained in the materials and method part of this document ^(f)Differences in the rate of mutation of the CMCT treated sample and untreated background sample. ^(g)The fold change in mutation rate caused by CMCT treatment, calculated as the ratio of the difference in mutation rates of the CMCT treated and untreated sample divided by the mutation frequency of the untreated sample.

TABLE 4 All C positions containing a difference in mutation rate > 2% CMC Background Differences in Fold Base^(a) RNA^(b) Modification^(c) Mutation Rate^(d) Mutation Rate^(e) Mutation Rates^(f) Change^(g) C 2505 23S OH5C 0.1482 0.0130 0.1352 10 C 1660 23S None 0.0889 0.0626 0.0263 0.4 ^(a)RNA bases position on the ribosomal RNA. ^(b)RNA molecule where the modification was observed. ^(c)The type of modification as previously determined. ^(d)Rate of mutation determined as explained in the materials and method part of this document. ^(e)Rate of mutation for the background sample as explained in the materials and method part of this document ^(f)Differences in the rate of mutation of the CMCT treated sample and untreated background sample. ^(g)The fold change in mutation rate caused by CMCT treatment, calculated as the ratio of the difference in mutation rates of the CMCT treated and untreated sample divided by the mutation frequency of the untreated sample.

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It should be borne in mind that all patents, patent applications, patent publications, technical publications, scientific publications, and other references referenced herein and in the accompanying appendices are hereby incorporated by reference in this application to the extent not inconsistent with the teachings herein.

While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims. 

What is claimed is:
 1. A method for detecting an RNA post-transcriptional modification in a sample, comprising: performing a reverse transcription reaction of an RNA in the presence of Mn²⁺ to generate cDNA, wherein the Mn2+ is at a concentration sufficient to induce a base misincorporation at a location of the RNA comprising a nucleoside modification; and performing next generation sequencing on the cDNA under conditions to detect the base misincorporation.
 2. The method of claim 1, wherein the nucleoside modification comprises of m2G (N2-methylguanosine), m3Ψ (3-methylpseudouridine), 5-hydroxylC (5-hydroxyl cytosine), m7G (7-methylguanosine), m4Cm (N4,2′-O-dimethylcytosine), m3U (3-methyluridine), m6,6 A (N6, N6-dimethyladenosine), m1G (1-methylguanosine), m6 A (N6-methyladenosine), Cm (2′-O-methylcytidine), Um (2′-O-methyluridine), Am (2′O-methyladenosine), Gm (2′-O-methylguanosine), Ψ (pseudouridine), m1A (1-methyladenosine), dihydrouridine (D) or a combination thereof.
 3. The method of claim 2, wherein the nucleoside modification comprises m2G (N2-methylguanosine), m3Ψ (3-methylpseudouridine), 5-hydroxylC (5-hydroxyl cytosine), m7G (7-methylguanosine), m4Cm (N4,2′-O-dimethylcytosine), m3U (3-methyluridine), m6,6 A (N6, N6-dimethyladenosine), m1G (1-methylguanosine), dihydrouridine (D) or a combination thereof.
 4. The method of claim 2, wherein the nucleoside modification comprises m6 A (N6-methyladenosine), m5U (5-methyluridine), Cm (2′-O-methylcytidine), Um (2′-O-methyluridine), Am (2′O-methyladenosine), Gm (2′-O-methylguanosine), Ψ (pseudouridine), m1A (1-methyladenosine), or a combination thereof.
 5. The method of claim 1, wherein performing the next generation sequencing comprises Converting the cDNA fragments into dsDNA; Fragmenting the dsDNA; and Performing sequencing on the dsDNA fragments that employs pyrosequencing, sequencing by ligation or sequencing by synthesis methodologies.
 6. A method for detecting an RNA post-transcriptional modification in a sample, comprising identifying one or more mutations in a DNA nucleic acid sequence in the sample made as a result of subjecting a RNA to reverse transcriptase in the presence of Mn2+; wherein a locus of a mutation of the one or more mutations represents a nucleoside modification.
 7. The method of claim 6, wherein the sample comprises a dsDNA library of fragments and further comprising performing next generation sequencing on the dsDNA library of fragments.
 8. The method of claim 7, wherein performing next generation sequencing on the dsDNA library of fragments comprises obtaining sequence data via pyrosequencing, sequencing by ligation or sequencing by synthesis methodologies; and aligning the sequence data to generate aligned sequence data.
 9. The method of claim 8 further comprising comparing the aligned sequence data to a reference sequence and calculating mutation frequencies in the aligned sequence data.
 10. The method of claim 6, further comprising identifying nucleoside modification type of the nucleoside modification based on a substitution pattern of the corresponding mutation.
 11. A reverse transcriptase buffer composition comprising a Tris compound; a potassium salt; a reducing agent; and a manganese salt.
 12. The composition of claim 11, wherein the Tris compound is Tris acetate or Tris hydrochloride.
 13. The composition of claim 11, wherein the manganese salt is manganese chloride or manganese acetate.
 14. The composition of claim 11, wherein the reducing agent is dithiothreitol.
 15. The composition of claim 11, wherein the potassium salt is potassium chloride or potassium acetate.
 16. The composition of claim 11, further comprising deoxynucleotide triphosphates (dNTPs).
 17. A reverse transcription kit comprising an amount of an reverse transcription buffer composition according to claim 7; and one or more of the following: (i) an amount of an RT primer containing composition; (ii) an amount of a dNTP containing composition; and (ii an amount of a reverse transcriptase containing composition.
 18. A method comprising Obtaining aligned sequence data of a RNA that has been subjected to reverse transcription in the presence of Mn2+ and next generation sequencing; Identifying one or more mutations in the aligned sequence data relative to a reference sequence; and Determining one of the following based on the identifying step: (i) a cell type in which the RNA was produced; (ii) whether a cell type in which the RNA was produced is cancerous; and (iii) whether the biological source of the sample is a twin of another sample.
 19. A screening method comprising Subjecting a cell to a test agent; Obtaining an RNA sample from the test agent; Determining whether the RNA sample comprises one or more nucleoside modifications by performing reverse transcription on the RNA sample in the presence of Mn²⁺ to produce a cDNA, performing next generation sequencing of the cDNA to produced aligned sequence data and identifying one or more mutations in the aligned sequence data relative to a reference sequence; Comparing the one or more nucleoside modifications from the RNA sample to a control RNA sample, wherein the control RNA sample is of same cell type but which has not been subject to the test agent; and Identifying the test agent as a nucleoside modulator if a number or type of nucleoside modifications in the RNA sample differs from the control RNA sample. 